The development of improved, highly efficient compression processes have become increasingly important in view of ever increasing costs for energy. Further, in various power generation processes, including some of those integrated with fuel synthesis processes, the compression of residual or by-product various gases, including carbon dioxide, is expected to become more important and increasingly prevalent as the call for sequestration of carbon dioxide becomes more urgent. Thus, a reduction in gas compression costs by providing a gas compressor having high efficiency would be desirable in a variety of gas compression applications. When compressing high molecular weight gases, energy reduction and thus cost reduction become especially important.
In general, design methods associated with prior art supersonic compressors have encountered various difficulties. Some structures previously suggested have had or would have difficulty, as a practical matter, in ingesting an oblique leading edge shock pattern, and thus, have not been suitable for reliable starting in supersonic operation. Most such difficulties are problematic, since in order to maintain low shock losses at increased relative Mach numbers, the use of some sort of oblique shock system is generally required. However, an oblique shock wave system is of value in supersonic gas compression since it ultimately enables the maintenance of an operational pre-normal shock Mach number that is sufficiently low so that the total pressure loss at the terminal normal shock wave is minimized, thus preserving efficiency.
As a consequence of trying to provide low loss supersonic shock compression while maintaining a self starting compressor design, compressor designs have had a practical compression ratio upper limit. This is because the level of geometric contraction required to achieve a low loss supersonic compression process upstream of the normal shock wave results in a throat size, i.e. the cross-sectional flow area of minimum size of the aerodynamic duct in which supersonic compression occurs, that will not start at inlet relative Mach numbers required to achieve pressure ratios above about 2.5 to 1. In other words, in prior art designs known to me, the area of the throat of a compression duct compared to the area of capture at the inlet of such compression has needed to remain relatively large, roughly in the 85% range or higher, in order to enable such a design to “self start” with respect to the supersonic shock waves attendant to such designs.
Due to the above mentioned limitations inherent in self-starting supersonic compressor design, a method for the design of a supersonic compressor that enables the simultaneous provision of high pressure ratios, at least in the range above about 2.5 to 1, and moreover from that threshold up to a range of about 25 to 1 or more, and with high adiabatic efficiency, has not heretofore been provided.
Consequently, there still remains an as yet unmet need for a method of design for an easily started supersonic compressor that is capable of operating at high compression ratios in a stable and highly efficient manner under supersonic conditions. In order to meet such need and achieve and provide a method for the design of supersonic compressors that can achieve such operations, it has become necessary to address the basic technical challenges by developing new methods for starting such a supersonic compressor system. Thus, it would be advantageous to provide supersonic compressors that achieve supersonic shock capture in a suitably configured apparatus, while providing very high gas compression efficiencies in normal operation. Moreover, it would be advantageous to accomplish such goals while providing a compressor with high pressure ratios suitable for a single stage compressor design.
The foregoing figures, being merely exemplary, contain various elements that may be present or omitted from actual apparatus that may be constructed to practice the methods taught herein. An attempt has been made to draw the figures in a way that illustrates at least those elements that are significant for an understanding of the various methods taught herein for design, construction, and operation of high efficiency supersonic compressors. However, various other actions in the design of supersonic compressors using removal of a portion of bypass gas for starting of the compressor may be utilized in order to provide a versatile gas compressor that minimizes or eliminates starting difficulties and/or efficiency losses heretofore inherent in supersonic compressor designs.